Fast-switching high-capacity optical switches are needed to realize an agile optical-core network that may adjust swiftly to changes in desired connectivity between edge nodes. It is known to use an aggregation of switch modules in a multi-stage arrangement to construct a high capacity optical core node using switch modules of smaller sizes.
Applicant's U.S. patent application Ser. No. 10/223,222 filed on Aug. 20, 2002 and titled “Modular High-Capacity Switch” describes a modular optical switch that includes a set of optical switch modules connected in a mesh structure, a master controller for the entire modular switch and a switch-module controller for each of the optical switch modules. The optical switch modules receive optical signals from source edge nodes and transmit optical signals to sink edge nodes. The master controller selects a path, using a simple or compound time-slot matching process, through the mesh of switch modules for each optical signal related to a connection request. The optical switch modules are fast switching, enabling the use of time-sharing schemes such as Time-Division-Multiplexing (TDM), and a master controller of the modular optical core node uses an efficient path-selection process. A hybrid modular switch may include both optical and electronic switch modules, a master controller, and a switch-module controller for each of the switch modules.
The use of a mesh structure where connections between two switch modules may be routed through an intermediate switch module requires internal expansion to compensate for the use of an intermediate switching step.
Scheduling connections in a multi-stage high-capacity switching node comprising fast bufferless switch modules and operating in a time-sharing mode, such as burst-switching mode or conventional time-division multiplexing mode, may require a scheduler of very high throughput. The use of intermediate switching requires a computationally intensive third-order time-slot matching process as described in the aforementioned patent application Ser. No. 10/223,222. While a mesh structure employing intermediate switching is quite efficient, it is still desirable to seek means for further reducing the structural and control complexity of high-capacity modular switching nodes, thus extending their scalability and reducing their cost.